Electromagnetic contactor



July 23, 1968 P. w. MORRELL ETAL 3,394,328

ELECTROMAGNET IC CONTACTOR Filed Sept. 50, 1966 4 Sheets-Sheet 1 July 23, 1968 P. w. MORRELL. SML 3,394,323

ELECTROMAGNET I C CONTACTOR Filed Sept. 50, 1966 4 Sheets-Sheet 2 y f l @AMM tlorneys July 23, 19 P. w. MORRELL ETAL 393%323 ELECTROMAGNET I C CONTAGTOR 4 Sheets-Sheet 5 Filed Sept. 30, 1966 O www/HM 1| www# mm.J Z ygSZi' Attorneys Juy 23, i968 is, W. Mmmm @TAL 3,394,328

ELECTROMAGNETIC CONTACTOR Filed Sept. 30, 1966 4 Sheets-Sheet 4 United States Patent Oce 3,394,328 Patented July 23, 1968 3,394,328 ELECTROMAGNETIC CONTACTOR Peter W. Morrell, Alan H. Mainwaring, and John B. Tyler, Wolverhampton, England, assignors, by mesne assignments, to Federal )Pacific Electric Company, Newark, NJ., a corporation of Delaware Filed Sept. 30, 1966, Ser. No. 583,328 8 Claims. (Cl. 335-167) ABSTRACT F THE DISCLOSURE An electromagnetic contactor including a ball as a latching element for preventing relative movement of the stationary and movable contact assemblies. Auxiliary contacts having an insulated housing are provided between the pairs of main contacts and the throw-off springs for the contactor engage the auxiliary contact housings to provide a compact unit.

This invention relates to electrical contactors of the type in which the main movable contact or contacts are moved to the closed position by electrically energising an operating coil (or in some cases more than one coil). The electromagnetic force which is produced by the energised coil acts on an armature. Normally the coil is iixed and the movement of the armature is transmitted to the movable contact or contacts by the contactor operating mechanism. The force which the coil must produce toV close the contacts needs to be quite considerable to ensure that good electrical contact is made between the xed and movable contacts. In addition this force has to be suificient to overcome the elfect of the contact or throwoff springs (or spring), the purpose of which is to separate the xed and movable contacts quickly when the operating coil ceases to be energised. Accordingly operating coils of contactors have to have a fairly high power rating to produce this force.

Many contactors however are used in situations where the contacts are held in the closed position for prolonged periods and in order to avoid the excessive power consumption which would occur under these circumstances, they are often tted with devices, known as latching 1devices, which cooperate with the operating mechanism to prevent the separation of the fixed and movable contacts when the operating coil is de-energised. With a contactor having such a device, the operating coil has only to be energised for a period suticient to close the contacts after which the latching device retains the contacts in the closed position.

Latching :devices take a number of different forms but all tend to suffer from the fact that the frictional contact which the latch makes with the operating mechanism renders the release of the latch a more power consuming operation than would be expected. Clearly the release of the latch has to occur fairly quickly once the need to open the contacts is apparent and often this must occur within stringent time limits. Sometimes the latch is arranged so as to be released through a hand-operated linkage but in many cases an electromagnetic device such as a solenoid is provided. The power which this mustexert clearly determines its overall size which, it is often desirable, should be as small as possible.

In one construction of conventional latching device, the latch is in the form of an arm which is pivoted at one end about a horizontal axis. The contactor operating mechanism includes a link which is also pivoted at one end about a parallel axis. This pivots from a substantially upwardly extending vertical position when the contactor is closed to a position separated from the vertical by about ten degrees when the contactor is open. When in the vertical position a projecting end of the latch engages behind the upper machined end of the link and retains it in that position. The latch is sprung into this position and the force exerted by the latch spring has to be overcome in order to release the latch to permit t-he contactor to open. Furthermore the frictional contact which the projecting end makes with the link results in a further frictional force which also has to be overcome. This latter force is dependent tol some extent on the pressure of the throw-olf and contact springs. Thus a lfairly large solenoid or like device is required to lift the latch while with a manually operated release, a quite considerable force has to be exerted particularly with the larger sizes of contactor. A further necessity with such a latching device is the services of a skilled fitter to adjust and maintain the correct tolerance 4between the projecting end of the latch and the link when the contactor is closed. It will be appreciated that this and the other difficulties mentioned lead to conventional latching devices being expensive to construct and maintain and they are often fairly large.

In accordance with the present invention a moving part of the operating mechanism of the contactor engages with a ball constituting part of the latching device which also includes a rst pivoted lever biased into contact `with a hook portion formed on a second lever pivoted about a parallel axis to the first lever, and a track along which the ball can move substantially transversely to the direction of movement of the moving part under the control of the second lever, the device being such that as the contactor contacts are closed and the moving part moves, the ball moves along the track into engagement with the moving part while the first lever pivots under `the effect of the bias and causes the second lever 4to pivot to a position in which the two levers engage one another in such a manner that the ball is prevented from being returned along the track by the eiect of the throw-off spring or springs when the operating coil is de-energised. The contacts are opened by pivoting the first lever against the bias until t-he hook portion slides over the iirst lever and thus permits the second lever to pivot under the influence of the throw-01T spring or springs to allow the ball to return along the track and the contacts to open.

With such a contactor, the effect of the ball and the two levers is that the bias applied to the first lever need only lbe very small so that very little effort is required to open the contactor. This is due to the fact that the trictional forces present in conventional latching devices are, surprisingly enough considerably reduced. A further improvement can be obtained by balancing the bias against the throw-off spring or springs as this reduces the force required to pivot the first lever when the contactor is to be opened further still. In addition fitting of the latching device is very simple as it is inherently self-aligning and does not involve adjustment to comply with stated tolerances. The device may be operated lby a solenoid or other electromagnetic device `but the arrangement of pivoted levers is particularly suited for operation by a push rod or Bowden cable.

In accordance with a further feature of the invention the contactor main movable contacts are spaced along an operating member and the contactor auxiliary movable contacts are located between the main movable contacts -along the member, and the contactor throw-oit spring or springs act on the operating mem-ber thereby serving to throw-off both the main and the auxiliary movable contacts. In conventional contactors the auxiliary movable contacts are generally controlled by projections on the moving part of the contactor and have their own throwoff springs. If one of these springs should fail or a projection, which may be in form of a moulding or linkage, break, then the auxiliary movable contacts may not operate with the main movable contacts thus giving rise to av false indication or false sequencing. This can have extremely serious results. The possi-bility of this occurring in a construction in accordance with the present invention -i-s however virtually eliminated due to the fact that the same throw-off springs control the auxiliary and the main movable contacts. Accordingly if the main contacts are in one position, the auxiliary contacts must be in a corresponding position.

By way of example a construction of electrical contactor in accordance with the present invention will now be described in more detail with reference to the accompanying drawings in twhich:

FIGURE 1 is an exploded side elevation of the contactor showing how it can be separated into two parts and with some of the internal components in dotted outline to illustrate the manner of operation;

FIGURE 2 is a front elevation of the contactor also with some of the internal components in dotted outline;

FIGURE 3 is 'a cross-section of the contactor taken along the line III-III of FIGURE 2;

FIGURE 4 is a front elevation partly in section of the right-hand part of the contactor as shown in FIGURE 1;

FIGURE 5 is a plan view of the underside of the contactor showing the latching device with which it is fitted;

FIGURE 6 is a fragmentary view similar to FIGURE 5 showing the latching device mechanism in the alternative position; and

v FIGURE 7 is la cross-section taken along the line VII- VII of FIGURE 5.

The illustrated contactor is designed for use with a H.P. 415 volts electric motor and is of Iwhat is known as the block type. It is constructed in two parts 1 and 2 best seen in FIG-URE l and which constitutes a twopart or two-piece assembly. The right-hand part 2 forms the lbase of Ithe contactor and is intended to be attached to a vertical surface so that the contactor is orientated as shown in FIGURE l. For example the base part 2 may be secured to a pair of generally horizontally extending bars as described in our British Patent No. 774,705.

The two parts 1 and 2 are held together by a pair of screwed bolts 3 which extend through the part 1 and screw into the part 2. This latter part contains the main contacts lan-d the auxiliary contacts all of which are operated by a common operating mechanism which includes a main contact arm 4. This arm 4 is moulded from a plastics material las are the respective -casings 50 and 51 of the parts 1 and 2. r

The part 1 includes an operating coil 6 having a vertical axis and securely fixed to the casing 50. The coil encircles the centre limb of a set of soft iron stampings 7 which also extend on either side of the coil and have Ithe shape Vof a letter E. The magnetic circuit constituted by the stam-pings 7 is completed by a further set of stampings 8 which are free to move in a vertical direction and also have the shape of a letter E. The stampings 8 constitute an armature and `are 'attached to lan arm 9 of a plastics material which has ends 60 which protrude through lrespective vertically extending slots 61 in the casing 50. A vertically aligned steel rod 36 having a shoulder 31 is secured to the arm 9.

A pair of bell-cranks 5 are pivoted to a rod S3, the ends of which are journalled in the casing 50. The bellcranks serve to transmit the vertical movement of the armature 8 to the main contact arm 4. It will be understood that when the coil 6 is not energised the operating mechanism is in the position shown in FIGURE 1 and both the main and the auxili-ary contacts are open. When the coil is energised however the armature 8 is attracted vertically upwards to complete the magnetic circuit. The resulting upward `vertical movement of the armature is Atransmitted to the main contact arm 4 which is thereby caused to move horizontally to the right to close the contacts.

The part 2 of the contactor contains terminals vfor all 'the contacts as will be described later. It also includes a 4 pair of terminals 80 which constitute the operating coil terminals and are best seen in FIGURE 4. Each of these terminals is electrically connected to a respective contact 81. The part 1 of the contactor contains cooperating contacts 32 which are each sprung mounted and are each connected to a respective end of the coil 6.

When the parts 1 and 2 of the contactor are secured together, the contacts 81 and 82 `are sprung into contact with one another and ensure electrical continuity from the terminals Si) to the coil 6. Y

It is clear from the foregoing description that the contactor can be opened for maintenancey or adjustment merely by removing the two bolts 3. As all the terminals are in the part 2 which may `be left secured to its normal support, no leads have to be disconnected and the procedure is extremely quick and easy. Furthermore the operating coil 6 is immediately available for testing and is of course disconnected from the normal supply by which it in energised. In fact if the coil is found to be faulty, a new part 1 can be secured to the p-art 2 to replace the original part 1 housing the faulty coil. During the replacement or inspection of the part 1 the main cont-act arm 4 is retained within the part 2 by a pair of plastic plates 83 (FIGURE 4) which are held covering the contacts by a pair of `bolts 84. The latter may vbe easily removed to give immediate access to the contacts if this is desired.

The arrangement of the contacts can best be understood from FIGURES 3, 4 and 7. The contactor has three pairs of main movable contacts 13 which make contact with three pairs of main fixed contacts 14 when the contactor is closed. The pairs of movable contacts are equally spaced along the main contact arm 4 as shown in FIG- URE 4. Part of the arm 4 is cut-away to show one pair of xed contacts 14. The other main fixed contacts are identical and similarly all the main movable contacts are identical.

Each of the main fixed contacts 14 is electrically connected to a respective termin-al 15 as shown in FIGURE 7. Reference to FIGURE 4 shows that three of these terminals are located on one side of the part 2 and the other three are located onthe other side. The three-phase supply is connected to the terminals on one side of the contactor while the electric motor or other load is connected to the terminals on the other side.

One pair of main mova'ble contacts 13 is shown in FIGURE 7. Each pair is secured to a metal plate 16 which has a reduced width central portion 17. The latter fits within a pair of walls 18 which are of integral construction with the main contact arm 4. The plate 16 is free to slide between the walls 18 in a horizontal direction :as viewed in FIGURE 7 but is biased towards the left by a compression spring 19 located between the arm 4 and a resilient metal strip 20 which 'bears on the plate 116.

When the contactor is closed each pair of main movable contacts 13 is in the position shown in FIGURE 7 with the three -springs 19 compressed and ensuring that good contact is made between the movable contacts 13 and the fixed contacts 14. The current path between each opposite pair of terminals 15 is completed with the current fiowing from one of the fixed contacts 14 to the cooperating Imovable contact 13, thence along the plate 16 to the other movable contact 13, and then to the other fixed contact 14.

When the contactor is open each of the three current paths between the opposite pairs of terminals 15 is broken in two places, that is to say the contactor is of the double-break type.

In addition to the main contacts, the part 2v of the contactor includes four pairs of auxiliary movable contacts 21 which make contact with four pairs of auxiliary fixed contacts 22 when the contactor is closed.

Two of the pairs of movable contacts 21 are supported by a plastics support 2.3 while the other two pairs of movable contacts 21 are supported by a second plastics sup- Each pair of auxiliary movable contacts 21 is secured to a respective metal plate 217, the two plates associate-d with each of the supports 24 and 25 `extending through the respective supports in which they are free to slide in a manner similar to the plates 1'6 between the walls 18. Compression springs 28 bias the plates V27 to the left as shown in FIGURE 3 andensu-re that good contact is made between the auxiliary'xe'd contacts 22 and the auxiliary movable contacts 21 when the contactor is closed. y

Each of the auxiliary iixed contacts 22 is electrically connected to a respective terminal 2.9, four of these terminals being on one side of the contactor as shown in FIG- URE 5 and the otherifour on the other side. When the contactor is open each of the four auxiliary circuits is broken in two places in a manner similar to the three main circuits.

During the rst movement of the main contact arm 4 to close the cont-actor, the two throw-oi springs 25 are compressed. After a certain amount of movement the main movable contacts 13 and the auxiliary movable contacts 21 simultaneously contact their respective xed contacts 14 and 22. Further movement of the main contact arm 4 results in compression of the three main contact springs 19 'and the four auxiliary contact springs 28. The throwoff springs 25 are compressed further so a quite considerable force has to be exerted in the latter stage of movement of the arm 4.

`It is apparent from the preceding description and in particular from FIGURE 4 that the location of the auxiliary contacts between the main contacts results in a compact form of contactor which is a considerable improvement over conventional contactors where the auxiliary contacts are often separate from the main contact assembly. More important however is the fact that the supports 23 and 24 are sandwiched between the main contact arm 4 and the pair of throw-off springs 25. This results in a positive movement of the auxiliary movable contacts which must, due to their very construction, move with the main movable contacts thus virtually eliminating the possibility of a fault in the contactor causing the auxiliary contacts to operate incorrectly.

The latching device in accordance with the invention is indicated generally at and holds the main contacts and the auxiliary contacts closed when the operating coil 6 is de-energised. Otherwise the armature 8 and the ar-m 9 would fall downwardly under the inuence of gravity and that of the contactor throw-od and contact springs. The latching device can be released when the contacts are to be opened etiher by energising a solenoid 48 housed within a casing 11 or by operating a mechanical release 12.

The latching device is best understood by reference to FIGURES 5, 6 and 7. As previously stated a rod 30 is attached to the arm 9 and moves upwards in a vertical direction as the operating coil 6 is energised. The shoulder 31 on the rod 30 engages with a steel ball 32 which constitutes part of the latching device 10. The latter includes a pair of mouldings 33 and 34 which are secured to the contactor casing 50 by bolts 36 and associated nuts 37. In FIGURES 5 and 6 the outer moulding 34 has been removed so as to show the components located in the space between the mouldings. These include a lever 38 which is pivoted at 39 about a vertical axis and a lever 40 which is pivoted at 41, also about a vertical axis. The lever 40 has at one end and on one side a hook portion 6 42 which contacts the end 43 of the lever 38. This latter lever is biased in a clockwise direction as viewed in FIG- URES 5 and 6 by a compression spring 44 which at one end ts into a recess 45 on the lever 38 and at the other end bears against the moulding 33. The lever 40 contacts the ball 32 and the arrangement of the two levers is such that the effect of pivoting the lever 3S in one direction is to cause the lever 40 to pivot in the opposite direction.

Each moulding 33 and 34 has a respective groove 46 and 47. The grooves are aligned with one another extending transversely to the direction of movement of the rod 30 and define a track or guide means for the ball 32. The latter is of such a size that it is restricted to this track.

The latching device operates as follows with the latch mechanism moving from the position shown in FIGURE 6 to that shown in FIGURE 5 as the contactor is closed. On energising the contactor operating coil 6 lthe armature 8 moves upwardly as viewed in FIGURE 7 and causes all the contacts to close. The rod 30 moves upwardly with the armature 8 and assumes the illustrated position. The eiect of the spring bias on the lever 38 is transmitted to the lever 40 which is thereby biased in an anti-clockwise direction and propels the ball 32 along the track into engagement with the shoulder 31 on the rod 30. As the two levers pivot, the end 43 of the lever 38 slides over the hook portion 42 to the position shown in FIGURE 5. When the operating coil 6 ceases to be energised the ball 32 prevents the rod moving downwards and thus holds the contactor closed. The manner in which the levers 38 and `40 engage one another prevents the downward force exerted by the shoulder 31 on the ball 32 causing the latter to return along the track. This downward force represents the weight of the armature assembly and the force exerted by the throw-off and Contact springs. It should be noted that the line of force exerted by the lever 40 acts substantially through the pivot point 39 of the lever 38.

When the contactor is to be opened the manual release 12 or the solenoid 48 (FIGURE 2) is actuated. The manual release consists of a Bowden cable secured to the solenoid support 91 at 92 and with the inner wire connected to the lever 38 at 92. The solenoid 48 has an armature 94 which slides from the position Ishown in FIGURE 5 to that shown in FIGURE 6 when the solenoid is energised. The armature 94 is connected to the lever 38 by a split pin 95.

Operation of either the cable 90 or the solenoid 48 pivots the lever 38 in an anti-clockwise direction against the effect of the compression spring 44. When the lever 38 has moved suiciently far, the hook portion 42 of the lever-40 slides over the end of the lever 38 thereby suddenly releasing the ball 32 which is propelled out of contact with the shoulder 31 by the force exerted by the latter. Accordingly the armature 8 moves downwardly and the contactor opens, the components of the latching device taking up the positions shown in FIGURE 6.

When the operating coil is subsequently energised the latching device again operates and the ball 32 is propelled into engagement with the shoulder 31. It is of course quite vital that the hook portion 42 should be so shaped as to enable the spring bias -to be transmitted to the lever 40 and an undercut rounded underside to the hook portion 42 as is illustrated is desirable in this respect.

The illustrated contactor is, as has been stated, intended for use with the magnet assembly acting in a vertical direction and the contacts moving in a horizontal direction.

This lresults in very little contact bounce as the contactor is closed and is clearly a very desirable feature.

We claim:

1. An electromagnetic contactor having a movable contact assembly and a cooperating stationary contact assembly, resilient means reacting between said assemblies to cause relative movement therebetween, operating means for said movable contact assembly including a movable member operatively connected to said movable contact assembly and movable along a given path, an operating coil for moving said movable member and said movable contact assembly from a first position to a second position when said coil is energized, and latching means for holding said movable contact assembly in said second position against the etiect of said resilient means when said operating coil is (le-energized, said latching means including a ball shiftable into latching engagement with said movable member, rst and second pivoted levers pivoted about parallel axes, means biasing said first lever into engagement with said second lever, guide means along which said ball can move substantially transversely to said path of said movable member under the control of said. second lever, said ball being moved into latc'hing engagement with said movable member by said second lever when said iirst lever is pivoted by said biasing means, said second lever pivoting to a position in which said two levers engage one another to prevent return movement of said ball along said guide means, whereby relative movement between said stationary contact assembly u and said movable contact assembly is prevented when said operating coil is cle-energized, and means for pivoting said iirst lever to effect release of said ball for return movement along said guide means.

2. A contactor according to claim 1 wherein said movable member has a shoulder against which said ball engages.

3. A contactor according to claim ll wherein an armature is provided within said operating coil and said movable member is attached thereto.

4. A contactor according to claim l wherein said first lever engages said second lever on one side thereof and said ball engages the other side.

5. A contactor according to claim 1 wherein said movable and stationary contact assemblies include both main contacts and auxiliary contacts respectively, said movable main contacts and movable auxiliary contacts being mounted on an operating member, said main movable contacts being spaced along said operating member and said auxiliary movable contacts being located between said main movable contacts along said operating member, said resilient means reacting between said movable and said stationary contact assemblies including throwoff springs, said throw-ott springs acting on said operating member thereby serving to throw-off both said main and said auxiliary movable contacts.

6. A contactor according to claim 5 wherein said auxiliary movable contacts are in sets one of which is located between each pair of main movable contacts, and wherein each such set is mounted on -an individual insulated subassembly, said subassembly being sandwiched between one of said throw-oit sprin-gs on one side and said operating member on the other side.

7. A contactor according to claim 6 wherein each set of auxiliary contacts includes vfour movable contacts, respective pairs of which being mounted on a conducting support extending through said insulated subassembly, said conducting supports being slidable in a direction parallel to the direction of movement of said operating member, said subassembly including contact pressure springs engaging said supports.

8. A contactor according to claim 1 wherein said contactor comprises a two-part assembly, a first part of said assembly including said movable and stationary contact `assemblies and forming the contactor base, said second part including said operating coil, said two parts being separable from one another.

References Cited UNITED STATES PATENTS 2,424,776 7/ 1947 Stapleton 335--253 2,540,976 2/1951 Weinreich 335-253 FOREIGN PATENTS 603,337 9/ 1934 Germany.

BERNARD A. GILHEANY, Primary Examiner.

H. B-ROOME, Assistant Examiner. 

